This invention relates to controls for windshield washers and particularly to such controls which use an electric pump to deliver a cleaning fluid to the windshield through a nozzle. Such a pump generally generates a nominally constant pressure in the fluid to force it through the nozzle at a certain nominal velocity, the nozzle directing the fluid at a particular target area of the windshield. This may be demonstrated by the path 15 shown in FIG. 1. However, the fluid, once free of the nozzle, is subject to the force of air moving across the vehicle windshield. This air, at high vehicle speeds, changes the trajectory of the fluid, thereby dislocating it from its intended path and forcing it to first contact the windshield in a lower area than the area to which it is projected at low vehicle speeds, as seen in the example of path 15' in FIG. 1. On the other hand, if the nozzle is directed to place the cleaning fluid on the windshield in the target area at high vehicle speeds, at low vehicle speeds it tends to project it higher on the windshield as in path 15" of FIG. 1 or, in extreme cases, completely over the windshield onto the vehicle roof when the vehicle is standing still. Thus, it is difficult to design a vehicle windshield washer system which places the cleaning fluid on the target area of the windshield at all vehicle speeds.
Many drivers have some experience with this problem; but the prior art has had little to say about it. The most typical solution has been similar to that shown in U.S. Pat. No. 3,089,204 to Fingeroot et al, issued May 14, 1963, which recognizes the problem and proposes a special nozzle design which breaks a fluid stream into a fine mist spray which is designed to spread over a wider area. Presumably, if the nozzle is designed to spread the cleaning fluid over a wider area of the windshield, at least some will be applied to the target area of the windshield at any vehicle speed. This is true to some extent. However, the distribution of cleaning fluid across the windshield still varies with vehicle speed, since the fine droplets are also subject to dislocation by the air stream rushing over the windshield.
U.S. Pat. No. 2,797,131 to Parkes, issued June 25, 1957, shows a windshield washer mechanism with a nozzle which is rocked up and down during the application of cleaning fluid to the windshield; however, the purpose is to cover a wider area of the windshield. Although the apparatus shown would inherently assist in applying some cleaning fluid to the windshield over a wider range of vehicle speeds, there is no recognition or teaching of this fact. In addition, this approach would be a cumbersome and expensive approach to the problem discussed herein.